The present invention relates to separate paper for a process and more particularly to separate paper having a release agent layer to be used in production of synthetic leather, hereinafter sometimes referred as to syn. leather.
Synthetic leather which has conventionally been produced includes polyurethane leather, semi-synthetic leather, poly(vinyl chloride) leather, and the like. Production of the polyurethane leather comprises steps of coating, drying and solidifying a synthetic resin, such as polyurethane or the like, in a paste state on a separate paper for a process and then laminating the solidified synthetic resin layer to a substrate cloth, if necessary, through an adhesive.
Further, known as a production method for the semi-synthetic leather is a method comprising steps of coating, drying and solidifying a polyurethane in a paste state on a separate paper for a process, then forming a foamed layer made of poly(vinyl chloride) or the like onto the solidified polyurethane, and after that, laminating the solidified synthetic resin layer to a substrate cloth, if necessary, through an adhesive.
As a production method for the poly(vinyl chloride) leather, a method applicable comprises steps of coating, heating and gelling a poly(vinyl chloride) sol on separate paper and then laminating the resultant foamed layer of the poly(vinyl chloride) on a substrate cloth, if necessary, through an adhesive.
An example of the conventional separate paper is, in case of employing it for polyurethane laser production, a separate paper (polypropylene type) for a process which comprises a substrate and a separate layer formed on the substrate by applying polypropylene in a thickness of 20 to 50 xcexcm.
Further, in case of producing the semi-synthetic leather or the poly(vinyl chloride) leather, available is a separate paper (a methylpentene-based resin type) for a process which comprises a substrate and a separate layer which is a single layer of a methylpentene-based resin in a thickness of 20 to 50 xcexcm formed on the substrate.
Further, also used is a separate paper (acrylic resin type) for a process which comprises a substrate and a separate layer formed by applying an acrylic resin in 20 to 120 xcexcm to the substrate.
The separate papers generally used in the prior arts are formed so as to have a variety of hills-and-valleys patterns by embossing them after formation of the aforementioned polypropylene, methylpentene-based resin or acrylic resin layer onto a substrate, or by in-line embossing them in the state that the resins are not completely solidified.
After that, a synthetic resin paste (hereinafter referred as to a resin paste) for synthetic leather is applied, dried, and solidified so as to fill the valley parts of the hills-and-valleys pattern formed on the separate paper with the paste, and then the obtained layer article is laminated on a substrate cloth.
In general, the resin paste to be used has a high viscosity. Thus, it is difficult to fill completely the valley parts of the pattern on the separate paper with the resin paste.
In order to prevent the air from entrapping in the valley parts, some techniques has been developed in the art, for example, that of using a furnisher roll for coating parts, or of lowering the viscosity of the resin paste to be used. However, only by such techniques, it is difficult to lessen the air-entrapping due to the configuration of the hills-and-valleys pattern.
The present invention has been developed in consideration of the above described situations and aims to provide separate paper for a process which prevents the air-entrapping between the separate paper and a resin paste to be applied at the time of producing synthetic leather and which is capable of producing synthetic leather precisely regenerating the desired normal pattern free from bubbles of undesirably entrapped gas.
In order to achieve the above mentioned purposes, the present invention provides separate paper or a process comprising a substrate and a separate layer formed in at least one side of the substrate, wherein a surface of the separate layer has polygonal shaped figures which are as a combination thereof a surface view of a repeated hills-and-valleys pattern of the separate layer, and at least one side of each polygon is set so as to be at an acute angle to the direction of applying a synthetic resin paste for forming synthetic leather on the separate layer.
In such separate paper, if the polygonal shaped figures which are as the combination thereof a surface view of the repeated hills-and-valleys pattern of the separate layer are (2+2n)-gonal shaped figures (wherein the reference character n denotes a natural number), it is preferable that at least one diagonal line of each polygon is parallel to the application direction of the synthetic resin paste for forming synthetic leather on the separate layer. On the other hand, if polygonal shaped figures which are a combination thereof a surface view of the repeated hills-and-valleys pattern of the separate layer are (1+2n)-gonal shaped figures (wherein the reference character n denotes a natural number) and each possesses an axial symmetry with the symmetric axis which has an apex of the polygon, it is preferable that the symmetric axis is parallel to the application direction of the synthetic resin paste for forming synthetic leather on the separate layer and the apex is positioned at the application starting-side in the polygon. Further, the separate layer may have a combination of the aforesaid two types of polygon shaped figures.
The present invention also provides separate paper for a process, comprising a substrate and a separate layer formed in at least one side of the substrate, wherein a surface of the separate layer has a combination of closed-outline figures which is a view of a repeated hills-and-valleys pattern, wherein a curved-line portion of the closed-outline figure is an out-curved convex curve and crosses the application direction of the synthetic resin paste for forming synthetic leather on the separate layer.
Further, the present invention provides separate paper for a process comprising a substrate and a separate layer formed in at least one side of the substrate, wherein the side faces of the valley part of the pattern on the separate layer are at an angle of 30 degrees or higher to the perpendicular line of the substrate.
Further, the present invention provides separate paper for a process comprising a substrate and a separate layer formed in at least one side of the substrate, wherein the side faces of the valley part forming the figure on the separate layer are at an angle of 0 degrees or higher to the perpendicular line of the substrate and wherein the crossing portions of the side faces and a bottom face in the valley part are radiused. In this case, the radiused portions preferably have 50 xcexcm or longer radius.
Also, in the separate paper for a process of the present invention, the plane portions of the surface of the separate layer are preferably a finely roughened face having an arithmetical mean roughness Ra of 1.5 to 30.0 xcexcm. Further, in this case the figures, i.e., the surface hills-and-valleys pattern of the separate layer preferably have a Ry of 10.0 to 100.0 xcexcm.